bpf: sockmap test remove shutdown() calls

bpf: sockmap test remove shutdown() calls

Currently, we do a shutdown(sk, SHUT_RDWR) on both peer sockets and
a shutdown on the sender as well. However, this is incorrect and can
occasionally cause issues if you happen to have bad timing. First
peer1 or peer2 may still be in use depending on the test and timing.
Second we really should only be closing the read side and/or write
side depending on if the test is receiving or sending.

But, really none of this is needed just remove the shutdown calls.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>